Encyclopedia of Engineering Geology

2018 Edition
| Editors: Peter T. Bobrowsky, Brian Marker


  • Arpita NandiEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-73568-9_53


The term “clay” is applied both to Earth materials with a particle size equal to or less than 0.005 mm and to those minerals that are microcrystalline, layered, hydrous aluminum phyllosilicates, occasionally with variable amounts of iron, magnesium, and alkali metals (Gillott 1968; West 2010). Therefore, cohesive soils may be composed of mixtures of clay minerals and clay-sized materials like quartz, feldspar, and carbonate. Both clay minerals and clay-sized particles are the product of weathering from pre-existing rocks and found on or near the earth surface.


Globally, clay-bearing sediments, also referred to as argillaceous sediments, make up about 60% of the Earth’s surface, with clay minerals comprising up to two-thirds of the components. The atomic structure of clay minerals involves two basic units, tetrahedral silicate sheets (Si+4 cation occurs in fourfold and tetrahedral coordination with oxygen) and octahedral hydroxide sheets (Al+3occurs in...

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© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of GeosciencesEast Tennessee State UniversityJohnson CityUSA